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W. J. WILKINSON AND B. HEDSTRO M.

BOAT DAVIT.

APPLICATION FILED MAY a. 1918 Patented May 13, 1919.

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BOAT DAVIT.

APPLICATION FILED MAY a. 19m

a a N m Patented May 13, 1919.

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WILLIAM J. WILKINSON, OF OAKLAND, AND BERNARD HEDSTROM, OF SAN FRANCISCO,

CALIFORNIA.

BOAT-DAVIT.

Specification of Letters Patent.

Patented May 13, 1919.

Application filed May 8, 1918. Serial No. 237,152.

ToaZZ whom it may concern:

Be it known that we, WILLIAM J. WILKIN- sorr and BERNARD HEDsTRoM, citizens f the United States, residing at Oakland, Alameda Co., and San Francisco, San Francisco 00., respectively, and State of California, have invented certain new and useful Improvements in Boat-Davits, of which the following is a specificatiton.

This invention relates to improvements in devices for hoisting and lowering boats over a shipsside and more particularly to a davit of the quadrant type.

The principal object of our invention is to provide a davit having a power controlled boom which is adapted to swing the boat a considerable distance from the side of the vessel. A further object of the invention is to so arrange the controlling mechanism for these booms'that when the free ends of the latter are in their outermost position the greatest amount of power is exerted by the operating mechanism to; control the movement thereof and as the boom assumes an upright position the amount of power necessary to cause the same movement is considerably less. Thus, at the point where the greatest Weight and consequently the greatest strain is imposed on the boom and associated parts, the power applied thereto is in direct proportion.

A further object 'of the invention is to provide a device of this character which is readily operated by a minimum number of persons and in which the weight of the boat will not in itself operate the lowering mechanism, thus preventing one boom from being suddenly lowered with the attendant danger of spilling out the occupants of the boat.

With these and other objects in view, the invention consists of certain novel features of construction, combinations and arrangements of parts hereinafter described and more specifically pointed out in the appended claims; it being understood that changes in form, proportion, size and minor details of construction within the scope of the claims may be resorted to without departing from the spirit of the invention or sacrificing any of the advantages thereof.

Referring to the drawing forming a part of this specification,

F lgure 1, is a view in end elevation showing the improved davit mounted on the deck of a vessel.

Fig. 2, is a view in front elevation, the mechanism at one end being in section.

Fig. 3, is a view in section on the line 3-3, Fig. 2.

Fig. 4k, is a view in side elevation showing a modified form of gear for operating the boom.

Referring to corresponding parts of the several views by the same numerals of reference, 1 denotes the boat'deck to which are attached, in any suitable manner, the right and left hand stands 2 and 3. These stands are similar in construction and the description hereinafter will apply for both. Each stand consists of a base plate 4 from which rise the sides 5 and 6 that in turn are connected by cross plates 30. These stands may be constructed of suitable structural shapes riveted or bolted together or they may be made of cast material. Near the top of .the frame is a shaft or pin 7 extending through from one side to the other, on which is pivotally mounted the boom 8. This boom is of sufficient length to extend outwardly overIthe edge of the boat deck and lower a boat to the water line even when the ship is listing to a considerable extent. As here shown it consists of two, channels placed back to back and riveted together, and to the joined webs we attach the flanged sleeve 34 to secure a large bearing on the pin 7. On the upper end of the boom is attached a curved head 9, the outer end of which is provided with alug 10. Pivotally attached to this lug is link member 11 and to the opposite end of the latter is pivotally attached a tackle block 12.

The boat is denoted by 13 and on each end is provided with suitable means for engagement with the hooks 14 which are attached to the lower tackle block 16. These blocks may have any required number of pulleys over which passes a rope or cable 17, the

free end of which is fastened arounda cleatv edge of which is eccentric with the shaft l. A segmental internal toothed gear 20 is provided having the same form as the edge of plate 19, and to which it is attached by bolts 32 extending through the plate and lugs 31 formed on the segment.

Secured to the side 6 is a stud bolt 22 on which is revolubly mounted the worm wheel 23 and the eccentric toothed gear 21. This worm and gear are in turn secured to each other and the eccentricity of the gear is such that it properly coacts with the segment 20. It will be understood that by eccentric we do not mean merely a circle which is off center from a given point, but include other curves which deviate from a circle and which may or may not have their centers in the axis of rotation.

Meshing with the wheel 23 is a helical worm 24 which is attached to a shaft 25 that has attached on its opposite end one side of the universal joint 33. Shaft 25 is revolubly mounted in bearings 26 which in turn are attached to the side 6. A short shaft 35 is revolubly mounted in a bearing 27 and in the plate 30 and on the inner end is attached to the other side of the universal joint and on the outer end has attached thereto the crank handle 28.

In the modified form shown in Fig. A, the toothed gear 40 which cooperates with the segment 11 is made in the form of a spiral, the center of which is the axis of shaft 22. By this arrangement the effect which we desire to obtain can be accentuated.

Assuming a boat to be positioned as shown, the operation is as follows :By turning the crank handle 28, the shafts 27 and 25 are rotated causing the worm 24 to turn the wheel 23 and hence the toothed gear 21. The latter in turn moves the segment 20 and so swings the boom 8 outwardly.

Now, each successive position of the arm, as the latter moves outwardly until it reaches a horizontal position, increases the force which the weight of the boat and its occupants exert on the inner end of the arm, and consequently through the toothed gears against the efiorts of the person who is operating the crank handle. As we construct the segment 20 eccentric with the pivotal point 7, the eccentricity being suchthat when the arm is substantially horizontal,

it will require su stantially the same effort to be exerted on the crank handle to move a given weight when the boom is horizontal as when it is man approximate vertical position.

It will also be apparent that byselecting the proper pitch for the threads of worm 2A, the mechanism will be irreversible, that is, the weight on the outer ends of the davits can never cause rotation of the worm and shaft in case the handle 28 is free.

We claim as new and wish to cover by Letters Patent 1. A davit comprising a stand, a boom pivotally mounted in said stand intermediate its ends, an eccentric toothed segmental gear carried by the inner end of said boom, a pivotally mounted eccentric toothed gear adapted to cooperate with the aforesaid gear, and means for rotating said last menmeans for moving said boom through vary-' ing angulardistances for a given move,-. ment ofthe driving mechanism.

4. A davit comprising apivotally mounted boom, a segmental toothed gear attached to said boom, an operating gear cooperating with said segmental gear,said gears having a pitch line eccentric to the axis of said boom, and means for rotating said operating gear.

5. A davit comprising a pivotally mounted boom, a toothed gear having a pitch line eccentric to the axis of said boom attached to said boom, a toothed gearadapted to drive the aforesaid gear, and means for driving said last mentioned gear.

6. A davit comprising a pivotally mount-v ed boom, a toothed gear carried thereby, a

cooperating toothed gear for.- driving the toothed segmental gear carried by said boom, an eccentrically mounted gear adapted to mesh with said segmental gear, a worm wheel movable with said last mentioned gear, a driving worm, and means for rotating said worm.

8. A davit comprising a pivotally mounted boom, a segmental toothed gear attached to said boom, an operating gear cooperating with said segmental gear, said gears having a varying pitch line so that said boom moves through different angular distances for a given angular movement of the operating gear, and means for rotating said operating gear.

9. A davit comprising a pivotally mounted boom, a toothed gear having a pitch line nonconcentric with the axis thereof attached to said boom, an operating gear having teeth adapted to cooperate with said first mentioned gear, and driving means for said operating gear.

10. A davit comprising a pivotally mounted boom adapted to swing from a substantially vertical position to a substantially horizontal position, a toothed gear carried by said boom, a drivin gear cooperating v therewith, said gears having a variable pitch ratio which decreases as the boom moves from vertical to horizontal, and means for rotating said driving gear.

11. A davit comprising a pivotally mounted, vertically movable boom, an internally toothed segmental gear carried by said boom, and having a pitch line non-concentric with the pivotal axis of said boom, an operating gear for driving said segmental gear, and an irreversible driving means for said operating gear.

12. A davit comprising a pivotally mounted boom, a segmental toothed gear attached to said boom, an operating gear cooperating with said segmental gear, said gears having a pitch line non-concentric to the axis of said boom, a worm wheel movable with said operating gear, a driving worm, and means for rotating said worm.

In testimony whereof we aifix our signatures.

WILLIAM J. WILKINSON. BERNARD HEDSTROM.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents Washington, D. G. 

